1. Technical Field
The present invention relates to an image display apparatus that projects and displays an image on a screen.
2. Description of the Background Art
Image display apparatuses such as projectors can project images on a projection screen for displaying the images. Such image display apparatuses have one or more connection terminals (e.g., VGA terminal) to which one or more information processing apparatuses such as personal computers (PCs) can be connected using cables. The connected information processing apparatuses transmit image data displayed on a display of the information processing apparatuses to the image display apparatus, and the image display apparatus projects such image data transmitted from the information processing apparatuses on the screen.
Such image display apparatus needs to conduct a given process when changing a projection image from one screen image of a first information processing apparatus, currently connected to the image display apparatus, to another screen image of a second information processing apparatus. For example, when projecting another screen image of the second information processing apparatus, the first information processing apparatus may be required to be disconnected at first, and then the second information processing apparatus is connected, which is not a convenient process for a user.
In view of such issues, JP-2009-180943-A discloses an image display apparatus such as a projector equipped with a plurality of input terminals connectable with a plurality of personal computers (PCs), in which the projector can display a screen image of each PC on a projection screen based on the image signals received via the input terminals. For example, when image signals are input at only one input terminal, the size of projection image of the input image signals is set to a full-screen size, and when image signals are input at the plurality of input terminals, the size of each projection image corresponding to each of input image signals is set to a ratio-based size based on the input image signals.
Such projector requires the input terminals corresponding to the numbers of PCs to display the screen image of each PC on the screen. Therefore, as the numbers of screen images of PCs to be displayed on the screen increase, the hardware size of connection circuit in the image display apparatus used for a plurality of PCs becomes large and complex.
With the development of wireless local area network (LAN), the image display apparatus can be equipped with a wireless communication function, with which the image display apparatus can communicate data with a plurality of information processing apparatuses simultaneously.
With employing the wireless communication function, the image display apparatus can communicate with a plurality of PCs simultaneously without using a plurality of input terminals, by which a hardware size of the connection circuit in the image display apparatus used for the plurality of PCs may not become too large.
However, each of the PCs cannot determine which PC corresponds to a target PC for the image display apparatus. Therefore, each PC may need to transmit image signals of screen images to the image display apparatus constantly. Therefore, as the numbers of connected PCs increase, data size received by the image display apparatus becomes too great, by which communication processing load of the image display apparatus increases.
JP-2006-92365-A discloses an image display apparatus to cope with such increased processing load. The image display apparatus connected to a plurality of terminal apparatuses receives a connection request from one of the terminal apparatuses, and displays a screen image of the terminal apparatus that has issued the connection request. Among the plurality of terminal apparatuses, a terminal apparatus that has issued the connection request at first can be set as a master terminal apparatus, and each of other terminal apparatuses is set as a non-master or slave terminal apparatus.
When the image display apparatus is under the operation based on a connection request from the non-master terminal apparatus, the master terminal apparatus can issue a connection request to the image display apparatus. Then, the image display apparatus restricts the connection request from the non-master terminal apparatus.
As such, conventional image display apparatus restricts the connection request from the non-master terminal apparatus once the image display apparatus is operated with the master terminal apparatus such as an information processing apparatus, which is the apparatus connected to the image display apparatus at first. In such a configuration, communications between the image display apparatus and the plurality of information processing apparatuses cannot be switched between active and non-active status from the image display apparatus so easily.